Absorbent article

ABSTRACT

An absorbent mixture, as made from fibers formed into a fibrous web and a polymerizable, cross-linkable material, in a liquid carrier. The material, when polymerized and cross-linked, results in a superabsorbent polymer. The material, in the liquid carrier, is dispersed within the fibrous web, as dispersed inclusions, and is polymerized and cross-linked in situ, within the fibrous web, so as to form a composite web comprising the fibrous web and the superabsorbent polymer, as dispersed particles, at least some of which are bound to fibers from the fibrous web. The composite web is ground, so as to cause some of the superabsorbent polymers to become particulate while fragments of the superabsorbent polymer remain bound to fibers from the fibrous web. Before the composite web is ground, it may be provided with a fibrous layer or fibrous layers in intimate contact therewith, and also compressed.

This application is a division, of application Ser. No. 07/772,772,filed Oct. 7, 1991, now U.S. Pat. No. 5,171,237, which is a division ofapplication Ser. No. 07/365,967, filed Jun. 14, 1989, now U.S. Pat. No.5,100,397.

TECHNICAL FIELD OF THE INVENTION

This invention pertains to an absorbent mixture comprisingsuperabsorbent particles and fragments of superabsorbent polymer boundto fibrous materials, and to an absorbent article including such amixture. This invention pertains also to a method of making such amixture. Since the absorbent mixture is capable of absorbing liquidhuman excreta, such as urine, menses, and wound excreta, the absorbentmixture may be advantageously employed in making an absorbent articleuseful in a disposable diaper, tampon, sanitary napkin, wound dressing,or similar article.

BACKGROUND OF THE INVENTION

Detailed discussions of absorbent articles employing superabsorbentmaterials in disposable diapers and other products are included inPieniak et al. U.S. Pat. Nos. 4,500,315, 4,540,454, 4,537,590, and4,573,988, which collectively provide useful background for thisinvention.

As discussed in the Pieniak et al. patents noted above, absorbentarticles can be advantageously made with absorbing layers and wickinglayers. The absorbing layers can be advantageously made from polyesterfibers, within which particles of superabsorbent material are dispersed.The wicking layers can be advantageously made from cellulosic fibers,which can include or be provided in the form of a densified, paper-likelayer, such as is disclosed in Burgeni U.S. Pat. No. 3,017,304, on oneside or each side. See, also, Mesek et al. U.S. Pat. No. 3,612,055 andRepke U.S. Pat. No. 3,938,522.

As also discussed in the Pieniak et al. patents noted above, thesuperabsorbent material can be advantageously formed from apolymerizable, cross-linkable material, e.g., a water-soluble monomerexemplified by sodium, potassium, or ammonium acrylate, which is coated,in a liquid carrier, e.g., in an aqueous solution, onto a fibrous web,and which is polymerized and cross-linked in situ, so as to form ahydrophilic polymer, which has superabsorbent properties.

Conventional coating techniques involve flooding the fibrous web withthe material, in the liquid carrier, while the fibrous web is supportedon a screen, so as to saturate the fibrous web, and exposing thesaturated web to a partial vacuum, which removes excess amounts of thematerial, in the liquid carrier. It has been heretofore known to removeexcess amounts of liquid by means of a padder or squeeze roll, after thefibrous web has been saturated, with similar results.

As an alternative to conventional coating techniques discussed above, ithas been heretofore known to spray droplets of such a material, in aliquid carrier, by means of nozzles.

It also has been heretofore known that polymerization and cross-linkingin situ can be advantageously effected by electron beam irradiation.Other techniques for polymerizing and cross-linking have been heretoforeknown, e.g., chemical initiation, which may require a catalyst orinitiator of a known type, and heating by conventional heating means.

Although the Pieniak et al. patents noted above disclose useful productsand useful methods of manufacturing such products, there has been aneed, heretofore, for absorbent articles offering superior wicking andabsorbent properties.

Herein, each reference to a polymerizable, cross-linkable material, in aliquid carrier, is intended to refer to any suitable monomer, oligomer,or polymer of low molecular weight, as exemplified by but not limited toa sodium, potassium, or ammonium salt of acrylic or methacrylic acid,together with a sufficient quantity of any catalyst or initiator neededto catalyze or initiate polymerizing and cross-linking of the monomer,oligomer, or polymer of low molecular weight, in a solution orsuspension in a liquid carrier, as exemplified by but not limited towater. Moreover, as and where appropriate, each reference to a polymeris intended to refer to a heteropolymer or a polymer of a usualstructure.

Herein, each reference to a material having absorbent properties isintended to refer to a material capable of absorbing liquid humanexcreta, such as urine, menses, or wound excreta. Moreover, eachreference to a material having superabsorbent properties is intended torefer to a material capable of absorbing many times its own weight ofsuch human excreta.

SUMMARY OF THE INVENTION

This invention provides an absorbent mixture having superior wicking andabsorbent properties. Broadly, the absorbent mixture comprises firstparticles, each comprised of a polymerized, cross-linked material havingabsorbent properties, and second, two-phase particles, each having afibrous phase comprised of fibers and a polymerized, cross-linked phasecomprised of fragments of such material bound to fibers of the firstphase. At least some of the first particles and at least some of thefragments are broken from larger particles of such material. Theabsorbent mixture may be advantageously employed in the manufacture ofan absorbent article useful in a disposable diaper, tampon, sanitarynapkin, wound dressing, or similar product requiring high absorbency.

According to this invention, the absorbent mixture is made from fibersformed into a fibrous body, e.g., a nonwoven web, and a polymerizable,cross-linkable material, in a liquid carrier. Fibers of many differenttypes are useful, such as rayons, cellulose esters, proteins,polyamides, polyesters, polyvinyls, polyolefins, polyurethanes, glass,and mixtures thereof. Polymerizable, cross-linkable materials of manydifferent types having absorbent or superabsorbent properties whenpolymerized and cross-linked, in liquid carriers, are useful, such as asodium, potassium, or ammonium salt of acrylic or methacrylic acid, inan aqueous solution wherein water is the liquid carrier. Such a salt,when polymerized and cross-linked, results in a superabsorbent polymer.

The polymerizable, cross-linkable material, in the liquid carrier, isdispersed within the fibrous body, as dispersed inclusions. Thepolymerizable, cross-linkable material is polymerized and cross-linkedin situ, within the fibrous body, so as to form a composite body. Thecomposite body comprises the fibrous body and the polymerized,cross-linked material, as dispersed particles, at least some of whichare bound to fibers from the fibrous web.

The absorbent mixture results from the composite body being ground, soas to cause some of the polymerized, cross-linked material to becomeparticulate, as powder or granules, whereby the first particles areformed, while fragments of the polymerized, cross-linked material remainbound to fibers from the fibrous body, whereby the second particles areformed. The material that becomes particulate and the material thatremains bound to fibers from the fibrous web account for thepolymerized, cross-linked material bound to fibers from the fibrous web,in the composite body before the composite body is ground.

The composite body may be optionally provided, before it is ground, withat least one layer of fibers formed into a fibrous layer in intimatecontact with the fibrous body having such inclusions. Such a layer maybe optionally provided on each side of the fibrous body having suchdispersed particles. If so, the fibers of the fibrous layer, or fibrouslayers, may be advantageously made from comminuted wood pulp. Thecomposite body may be intermediately processed, e.g., compressed, beforethe composite body is ground.

Fragments of the polymerized, cross-linked material remain bound tofibers from the fibrous body and strengthen the fibers to which suchfragments are bound, whereby particulates having fibrous matricesincluding such strengthened fibers tend to retain their bulk when wettedwith a liquid being absorbed, e.g., with urine being absorbed in adisposable diaper. Hence, the absorbent mixture exhibits superiorwicking properties with less tendency for gel blocking. Gel blockingoccurs if particles of a superabsorbent polymer tending to form a gelwhen swelling with a liquid being absorbed are too densely distributedwithin an absorbent article, so that the swelling particles tend to forma gel layer, which blocks additional liquid from penetrating.

The absorbent mixture exhibits superior absorbent properties, not onlyin terms of its efficiency as absorbent material but also in terms ofits rate of absorbency, particularly as compared to absorbent structurescontaining similar amounts of fibers of the same types and in the sameratios and similar amounts of a superabsorbent polymer of the same type,on a weight basis. The absorbent mixture may be advantageously employed,therefore, in the manufacture of an absorbent article useful in adisposable diaper, tampon, sanitary napkin, wound dressing, or similarproduct benefiting from superior absorbency.

These and other objects, features, and advantages of this invention areevident from the following description of a preferred mode for carryingout this invention with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram representing certain steps in the manufactureof an absorbent mixture according to this invention.

FIG. 2 is a fragmentary view taken along one edge of an absorbentarticle including layers of an absorbent mixture manufactured asrepresented in FIG. 1.

FIG. 3 is a graph showing comparative properties of two samples, onebeing a sample of an absorbent mixture according to this invention.

DETAILED DESCRIPTION OF PREFERRED MODE

While the present invention is susceptible of embodiment in variousforms, there is shown in the drawings and will hereinafter be describeda presently preferred embodiment, with the understanding that thepresent disclosure is to be considered as an exemplification of theinvention and is not intended to limit the invention to the specificembodiment illustrated.

This invention provides an absorbent mixture A comprising a novelmixture of particles of two types, which may be conveniently calledfirst and second particles, and having superior wicking and absorbentproperties.

Each of the first particles is comprised of a polymerized, cross-linkedmaterial having absorbent properties, preferably a superabsorbentpolymer of a known type used in disposable diapers, tampons, sanitarynapkins, or wound dressings, e.g., sodium, potassium, or ammoniumpolyacrylate produced by polymerizing and cross-linking a sodium,potassium, or ammonium salt of acrylic or methacrylic acid, as providedin an aqueous solution wherein the salt has been partially neutralized,and wherein the liquid carrier is water. A preferred example of such asolution is a 65% concentration (by weight) of a 55% neutralized (on amole basis) potassium salt of acrylic acid, as neutralized with a 45%potassium hydroxide solution.

Each of the second particles has a fibrous phase comprised of fibers anda polymerized, cross-linked phase comprised of fragments of thepolymerized, cross-linked material bound to fibers of the fibrous phase.At least some of the first particles and at least some of the fragmentsare broken from larger particles of such material. This invention allowsfor possibilities that some of the first particles, some of thefragments, or both are unbroken. The absorbent mixture A can beadvantageously made by a method to be next described.

Initially, a fibrous web W is provided along with a polymerizable,cross-linkable material, in a liquid carrier, from any suitable sourceS. When polymerized and cross-linked, the polymerizable, cross-linkablematerial results in the polymerized, cross-linked material noted above.Thus, an aqueous solution according to the preferred example noted abovemay constitute the polymerizable, cross-linkable material, in the liquidcarrier.

The fibrous web W is formed of fibers selected from rayons, celluloseesters, proteins, polyamides, polyesters, polyvinyls, polyolefins,polyurethanes, glass, or mixtures thereof. Preferably, the fibrous web Wcomprises poly(ethylene terephthalate) fibers of a type having a hollowcore, as available commercially under the trademark HOLLOFIL from E. I.DuPont de Nemours and Company, Wilmington, Del., and sheath-core fibers,each having a core of poly(ethylene terephthalate) and a sheath ofpolyethylene, as carded into a nonwoven web having a basis weight of 1.2oz/yd² and thermally bonded by subjecting the nonwoven web to air heatedto about 275° F. and pulled through the nonwoven web while the nonwovenweb is supported on a screen (not shown) in a known manner.

In a dispersing zone Z₁, the polymerizable, cross-linkable material, inthe liquid carrier, is dispersed within the fibrous web W, as dispersedinclusions including the liquid carrier. Conventional coating techniquesor alternative spraying techniques are useful to disperse thepolymerizable, cross-linkable material, in the liquid carrier, withinthe fibrous web W.

Conventional coating techniques involve flooding the fibrous web W withthe polymerizable, cross-linkable material, in the liquid carrier, whilethe fibrous web W is supported on a screen (not shown), so as tosaturate the fibrous web W, and exposing the saturated web W to apartial vacuum, which removes excess amounts of the polymerizable,cross-linkable material, in the liquid carrier. Excess amounts of liquidmay be alternatively removed by means of a padder or squeeze roll (notshown), after the fibrous web W has been saturated, with similarresults. Whichever approach is used to remove excess amounts of liquid,the fibrous web W tends to retain the polymerizable, cross-linkablematerial, in the liquid carrier, as dispersed inclusions including theliquid carrier, bridging adjacent fibers of the fibrous web W, and beingheld by fiber-to-fiber capillaries.

If alternative spraying techniques are used to disperse thepolymerizable, cross-linkable material, in the liquid carrier, withinthe fibrous web W, droplets of the polymerizable, cross-linkablematerial, in the liquid carrier, may be thus sprayed, as by means ofnozzles, onto opposite sides of the fibrous web W as the fibrous web Wis moved through the dispersing zone Z₁. The fibrous web W tends toretain such droplets as dispersed inclusions including the liquidcarrier, bridging adjacent fibers of the fibrous web W, and being heldby fiber-to-fiber capillaries.

After the polymerizable, cross-linkable material M, in the liquidcarrier, has been dispersed within the fibrous web W, as dispersedinclusions including the liquid carrier, the fibrous web W retainingsuch inclusions is moved to a polymerizing and cross-linking zone Z₂, inwhich the material M is polymerized and cross-linked in situ, within thefibrous web W, so as to form a composite web W comprising the fibrousweb W and the polymerized, cross-linked material, as dispersedparticles, some most, or all of which are bound to fibers from thefibrous web W. This invention allows for a possibility that some of thedispersed particles may not be so bound but may be loosely retainedwithin the composite web W'. However, dispersed particles bound tofibers from the fibrous web W constitute the larger particles notedabove, from which at least some of the first particles and at least someof the fragments are broken.

Any suitable means (not shown) for electron beam irradiation ispreferred as a means for polymerizing and cross-linking the material M;an example is an Energy Sciences™ (Model CB300) accelerator, asavailable from Energy Sciences, Inc. If electron beam irradiation isused, the fibrous web W retaining the material M, in the liquid carrier,in dispersed inclusions may be initially exposed to 2 MRAD of suchradiation on each side of the fibrous web W, and finally exposed to acuring dose of 8 MRAD on each side of the fibrous web W. Any othersuitable technique for electron beam irradiation may be instead used.

Any other suitable technique for polymerizing and cross-linking thematerial M in situ may be instead used, e.g., chemical initiation, whichmay require a catalyst or initiator of a known type.

The composite web W' contains dispersed particles of the polymerized,cross-linked material M from which substantially all of the liquidcarrier has evolved. If the polymerizable, cross-linkable material, inthe liquid carrier, is an aqueous solution according to the preferredexample given above, such particles are comprised of sodiumpolyacrylate, from which substantially all of the liquid carrier, i.e.,water, has evolved.

The composite web W' may be intermediately processed in known ways. Thecomposite web W' may be provided, on each side, with a fibrous layer,e.g., a nonwoven layer of fibers from comminuted wood pulp or othercellulosic fibers, in intimate contact with the fibrous web having suchinclusions of the polymerized, cross-linked material. The facing layersmay be also provided with a densified, paper-like layer (not shown) in amanner disclosed in the Burgeni, Mesek et al., and Repke patents notedabove. Moreover, the composite web W' may be then compressed, so as toincrease its density.

It is to be here understood that the composite web W' is made and may beintermediately processed by methods similar to methods disclosed in thePieniak et al. and other patents noted above. Thus, the composite web W'is useful apart from this invention, as an absorbent article of a typedisclosed in the Pieniak et al. patents noted above.

According to this invention, however, the composite web W', after anysuch intermediate processing step has been completed, is moved to agrinding zone Z₃, in which the composite web W' is ground, as by meansof a grinding mill (not shown), so as to form the first and secondparticles. At least some of the dispersed particles retained by thecomposite web W' are broken, as the composite web W' is ground, so as toproduce the first particles from the broken particles that had beenbound to fibers from the fibrous web W', from any broken particles thathad been retained by the composite web W' but were not bound to fibersfrom the fibrous web W, and from any particles that had been retained bythe composite web W' but were not bound to fibers from the fibrous web Wand were not broken, and so as to form the fragments bound to fibersfrom the fibrous web W from the broken particles that had been bound tofibers from the fibrous web W and from any particles that had been boundto fibers from the fibrous web W but were not broken.

Preferably, the absorbent mixture A comprises, on a weight basis, about5 to 40% of fibers from the fibrous web W, more preferably about 10% offibers from the fibrous web W, with the balance consisting essentiallyof a superabsorbent polymer. More preferably, the absorbent mixture Acomprises, on a weight basis, about 10% of fibers from the fibrous webW, also about 30 to 80% of the superabsorbent polymer, most preferablyabout 50% of the superabsorbent polymer, as particles, i.e., powder orgranules, and about 10 to 60% of the superabsorbent polymer, mostpreferably about 40% of the superabsorbent polymer, as fragments boundto at least some fibers from the fibrous web W. A most preferredcomposition for the absorbent mixture A, on a weight basis, is,therefore, about 10% of fibers from the fibrous web W, about 50% of thesuperabsorbent polymer, as particles, i.e., powder or granules, an about40% of the superabsorbent polymer, as fragments bound to at least somefibers from the fibrous web W.

When the composite web W is ground, fragments of the polymerized,cross-linked material M remain bound to fibers from the fibrous web Wand strengthen the fibers to which such fragments are bound. Particlesproduced by grinding of the composite web W' with fibrous phasesincluding such strengthened fibers tend to retain their bulk when wettedwith a liquid being absorbed by the polymerized, cross-linked materialM, e.g., with urine being absorbed in a disposable diaper. Since theliquid can channel through the absorbent mixture by capillary action tobe then absorbed by the polymerized, cross-linked material M, theabsorbent mixture A exhibits superior wicking properties with lesstendency for gel blocking, which is explained above.

Furthermore, the absorbent mixture A exhibits superior absorbentproperties, not only in terms of its efficiency as absorbent materialbut also in terms of its rate of absorbency, as compared to a compositeweb comprising fibers of the same types and in the same ratios and asuperabsorbent polymer of the same type, for equivalent basis weights ofthe superabsorbent polymer.

As shown fragmentarily in FIG. 2, an absorbent article 10 useful in adisposable diaper having conventional backing and facing layers (notshown) comprises a relatively thick, nonwoven fibrous layer 12 of fibersfrom comminuted wood pulp, a relatively thick layer 14 of a ground,absorbent mixture according to this invention, in intimate contact withthe fibrous layer 12, an intermediate layer 16 of a composite websimilar to the composite web described above, in intimate contact withthe layer 14 of the absorbent mixture, and a relatively thin, nonwoven,fibrous layer 18 of fibers from comminuted wood pulp. In FIG. 2, theintermediate layer 16 of a composite web and the layer 14 of theabsorbent mixture are demarcated approximately by dashed lines.

As one example, the absorbent article 10 may be advantageously made bycasting the relatively thin, nonwoven, fibrous layer 18 with a basisweight of 2.6 oz/yd² onto one expansive surface of the composite web toconstitute the intermediate layer 16, such web having a basis weight of1.2 oz/yd² and an add-on ratio of 3:1, inverting the resulting two-layerstructure, distributing the relatively thick layer 14 of the ground,absorbent mixture with a basis weight of 9.7 oz/yd² after grinding ontothe opposite surface of the fibrous layer 18, and casting the relativelythick, nonwoven, fibrous layer 12 with a basis weight of 5.2 oz/yd² ontothe exposed, expansive surface of the layer 14 of the ground, absorbentmixture. Desirably, the relatively thin, nonwoven, fibrous layer 18tends to retain any small particles that tend to sift from the layer 14of the ground, absorbent mixture through the composite web constitutingthe intermediate layer 16. In the example, the ground, absorbent mixtureresults from grinding a composite web with a basis weight of 1.2 oz/yd²and an add-on ratio of 10:1, before grinding. The composite web toconstitute the intermediate layer 16 may be pre-compressed, i.e.,compressed before the relatively thin, nonwoven, fibrous layer 18 iscast. All basis weights noted above are approximate.

Although the absorbent article 10 has been described as having layers,it is to be here understood that the materials of such layers tend tocommingle. As an example, some of the ground, absorbent material of thelayer 14 tends to migrate into the fibrous structure of the compositeweb constituting the layer 16. All references herein to layers areintended to be so understood.

In the absorbent article 10, the fibrous layers 12, 18, are regarded aswicking layers even if either such layer tends to remain dry, whereasthe layers between the fibrous layers 12, 18 are regarded as absorbinglayers. Such designations of layers as wicking layers and absorbinglayers are not intended as limiting, however, since the fibrous layers12, 18, ordinarily exhibit some absorbency and the fibers of the layersbetween the fibrous layers 12, 18, have good wicking capabilities. Theabsorbent article 10 exhibits a gradient of different absorbencies atits respective layers. In a disposable diaper, the thicker, fibrouslayer 12 is to be preferably disposed so as to face the backing layer,which is liquid-impervious, not the facing layer, which isliquid-pervious.

For comparable amounts of a superabsorbent polymer, the absorbentarticle 10 provides numerous advantages over absorbent articles knownheretofore. Thus, the absorbent article 10 exhibits a faster rate ofabsorbency, which may be plausibly explained by different rates ofabsorbency within the absorbent article 10, particularly in the ground,absorbent material constituting the layer 14 and the composite webconstituting the layer 16. Also, the absorbent article 10 exhibits lessleakage, which may be similarly explained. A greater portion of thesuperabsorbent polymer tends to contact the fibrous material of theabsorbent article 10, particularly the relatively thick, nonwoven,fibrous layer 12, which acts as a wicking layer. The relatively thin,nonwoven, fibrous layer 18 tends to remain drier.

Moreover, the superabsorbent polymer tends to swell to a highercapacity, which tends to be less restricted by the fibrous materials,particularly in the ground, absorbent material constituting the layer14. The higher capacity of the superabsorbent polymer provides theabsorbent article 10 with a higher capacity and with less tendency toleak. Furthermore, since much of the superabsorbent polymer is presentin the ground, absorbent material constituting the layer 14, rather thanin the composite web constituting the layer 16, there is less need forsoftening, or tenderizing, to condition the absorbent article 10 for itsuse in a disposable diaper.

As developed from comparative tests, FIG. 3 is a graph plotting, foreach of two samples, absorbency of a test liquid versus time. The testliquid, for each of these samples, was an aqueous solution of 1% byweight of sodium chloride. Absorbency was measured as demand absorbency,under a sample pressure of 0.5 psig and a 1.5 cm negative head of thetest liquid. The absorbed volume was measured after one minute and afterthree, five, nine, twenty, and thirty minutes, as indicated on thegraph. Demand absorbency was measured as described in McConnell U.S.Pat. No. 4,357,827.

In FIG. 3, the upper plot represents a first sample, of an absorbentmixture according to this invention, as made from a fibrous webcomprising fibers of a type having a hollow core, as availablecommercially under the trademark HOLLOFIL from E. I. DuPont de Nemoursand Company, Wilmington, Del., as carded into a nonwoven web having abasis weight of 1.2 oz/yd² and thermally bonded by subjecting thenonwoven web to air heated to about 275° F. and pulled through thenonwoven web while the nonwoven web was supported on a screen, and anaqueous solution of 65% concentration (by weight) of a 55% neutralized(on a mole basis) potassium salt of acrylic acid, as neutralized with a45% potassium hydroxide solution.

The fibrous web was flooded with the aqueous solution, while the fibrousweb was supported on a screen, so as to saturate the fibrous web. Thesaturated web was exposed to a partial vacuum, which removed excessamounts of the aqueous solution. The material in the aqueous solutionwas polymerized and cross-linked in situ, within the fibrous web, so asto form a composite web. The material in the aqueous solution waspolymerized and cross-linked by electron beam irradiation with aninitial exposure of 2 MRAD on each side of the fibrous web and with acuring dose of 8 MRAD on each side of the fibrous web.

The composite web was ground into particulates, so as to form the firstsample, which on a weight basis consisted essentially of about 10% ofthe fibers from the fibrous web, about 50% of the polymerized,cross-linked material, as particles, and about 40% of the polymerized,cross-linked material, as fragments bound to at least some fibers fromthe fiberous web. The polymerized, cross-linked material present in thefirst sample is a typical example of a superabsorbent polymer, as usedin disposable diapers and other products requiring high absorbency.

In FIG. 3, the lower plot represents a second sample, which consistedessentially of a composite web containing polymerized, cross-linkedmaterial like the composite web containing polymerized, cross-linkedmaterial in the first sample, the polymerized, cross-linked material inthe second sample having a basis weight about equal to the basis weightof the polymerized, cross-linked material present in the first sample.The second sample was not ground into particulates.

It has been concluded, from the results plotted in FIG. 3, that anabsorbent mixture according to this invention has superior absorbentproperties, not only in terms of its efficiency as absorbent materialbut also in terms of its rate of absorbency, as compared to otherstructures containing a superabsorbent material of the same type, forequivalent basis weights of the superabsorbent material.

From the foregoing, it will be observed that numerous modifications andvariations can be effected without departing from the true spirit andscope of the novel concept of the present invention. It is to beunderstood that no limitation with respect to the specific embodimentillustrated herein is intended or should be inferred. The disclosure isintended to cover by the appended claims all such modifications as fallwithin the scope of the claims.

What is claimed is:
 1. An absorbent article comprising a first absorbentlayer and a second absorbent layer, said first absorbent layercomprising (a) first particles, each comprised of a polymerized,cross-linked material, and (b) second, two-phase particles, each havinga fibrous phase comprised of particles of fibers and a polymerized,cross-linked phase comprised of fragments of said cross-linked materialbound to particles of fibers of the fibrous phase, said first particlesbeing loosely dispersed within said second particles, said secondabsorbent layer including a fibrous body and inclusions of saidcross-linked material, as polymerized and cross-linked in situ withinthe fibrous body of said second absorbent layer, the first and secondparticles being distributed in intimate contact with an expansivesurface of the second absorbent layer.
 2. An absorbent articlecomprising a first absorbent layer and a second absorbent layer, saidfirst absorbent layer being formed from a fibrous body includingpolymerized, cross-linked material having absorbent properties, at leastsome of which material is bound to fibers of said fibrous body, saidfirst absorbent layer comprising (a) first particles, each comprised ofsaid polymerized, cross-linked material, and (b) second, two-phaseparticles, each having a fibrous phase comprised of particles of saidfibers, and a polymerized, cross-linked phase comprised of fragments ofsaid cross-linked material bound to the particles of fibers of thefibrous phase, wherein at least some of the first particles and at leastsome of the fragments are broken from larger particles of saidcross-linked material after said cross-linked material is bound to thefibers from which said particles of fibers of said fibrous phase areformed, said first particles being loosely distributed within saidsecond particles, wherein said fibers from which said particles offibers are formed are first formed in said fibrous body and saidcross-linked material is provided in a liquid carrier beforepolymerizing and cross-linking, said material being dispersed within thefibrous body as dispersed inclusions, including the liquid carrierbefore polymerizing and cross-linking, and being polymerized andcross-linked in situ, within the fibrous body, so as to form a compositebody comprising the fibrous body and the polymerized, cross-linkedmaterial, as dispersed particles, at least some of which are bound tothe fibers from the fibrous body, the composite body being ground so asto cause some of the polymerized, cross-linked material from thedispersed particles to become particulate, whereby said first particlesof cross-linked material are formed, while fragments of the polymerized,cross-linked material from the dispersed particles remain bound to theparticles of fibers from the fibrous body, whereby the second two-phaseparticles are formed, said second absorbent layer including a fibrousbody and inclusions of said cross-linked material, as polymerized andcross-linked in situ within the fibrous body of said second absorbentlayer, the first and second particles of the first absorbent layer beingdistributed in intimate contact with an expansive surface of the secondabsorbent layer.
 3. The absorbent article of claim 2 wherein saidmaterial, as polymerized and cross-linked, is a superabsorbent polymer.4. The absorbent article of claim 2 further comprising a wicking layerof fibrous material in intimate contact with an expansive surface of oneof the absorbent layers.
 5. The absorbent article of claim 4 whereinsaid material, as polymerized and cross-linked, is a superabsorbentpolymer.
 6. The absorbent article of claim 2 further comprising a firstwicking layer of fibrous material in intimate contact with an expansivesurface of the first absorbent layer and a second wicking layer inintimate contact with an expansive surface of the second absorbentlayer.
 7. The absorbent article of claim 6 wherein said material, aspolymerized and cross-linked, is a superabsorbent polymer.
 8. Atwo-phase, absorbent particle having a fibrous phase comprised offibers, and a polymerized, cross-linked material bound to fibers fromthe fibrous phase, dispersing a polymerizable cross-linkable material,in a liquid carrier, within a fibrous body, polymerizing andcross-linking the polymerizable, cross-linkable material in situ, withinthe fibrous body, so as to form a composite body, said composite bodycomprising the fibrous body and dispersed particles of the polymerized,cross-linked material bound to fibers from the fibrous body; andsubdividing the fibrous body to form said particle.
 9. A two-phase,absorbent particle according to claim 8 wherein the composite body issubdivided by grinding to form said particle.
 10. A two-phase absorbentparticle according to claim 9, in an absorbent mixture with additionalparticles, which include similar two-phase absorbent particles andparticles of the polymerized, cross-linked material, with the particlesof the polymerized, cross-linked material being dispersed freely in theabsorbent mixture.